The goals of the University of Chicago Cancer Research Center Animal Barrier Facility are multifold. The Facility provides to any investigator the means to perform animal studies using specific pathogen-free mice and rats. In addition, the Facility provides expertise in viral analyses of biological materials that are introduced into the animals and is capable of performing laboratory analyses of mice maintained in the facility. The Animal Barrier Facility in FMI is an essential component of the Cancer Research Center, providing a quality barrier facility (approximately 6,800 sq ft) to investigators requiring mice free from adventitious agents. The Facility contains seven animal rooms each equipped with three Illinois cabinets capable of housing approximately 1,260 cages or 5,040 adult mice (single shelved). These animal rooms, along with a laboratory, a procedure room and a dedicated pass through cage washing and autoclave area, are situated within a supply and return corridor system. Pass-through lockers with shower facilities are used to access the supply corridor and clean service areas. An office and support areas for feed, bedding and storage complement the Facility. Elevator access is limited, and a separate delivery deck is used to accept mice to be housed in this Facility. Microisolator caging systems are employed throughout the barrier. All cages along with bedding are autoclaved prior to entry into a room. Animals are transferred within a separate hood or within the Illinois cabinet by the animal care staff, using chemically treated forceps between cage transfers. A maximum of four adult mice are permitted per cage, and cages are changed twice weekly. Colony animals are maintained in "red rooms" which are entered only by animal care staff. these animals are brought to experimental rooms by animal care staff on request. A bar coded entry computer system provides accurate and detailed census information on a weekly basis when requested by investigators. The quality control and preventive medical programs are overseen through the veterinary faculty. The health quality control program is designed to detect statistical variances from established norms at specific infectious disease prevalence levels and at specific time intervals. This program employs sentinel animals monitored monthly and quarterly, serum banking, evaluation of "index" cases and close communications with investigators who may note unexplained variances in their experiments.